I have an old (1947±) LeBlonde Regal lathe. The huge motor (G.E. probably
only 2 hp) has grease fittings on each end (motor housing). Do I really use
grease? Do I replace the zerks with cups and add oil? Or do I modify my
grease gun to use oil?
All advise appreciated.
Ivan Vegvary
Hi Ivan,
I used to run an early '60s Devlieg jig mill at work with a huge motor that
also had grease fittings at each end. We did (and still do) use grease in
it. Ours has plugs on the opposite side of the housing from the zerks that
need to be removed before new grease is added or you'll blow out the seals
and pump the motor full of grease. We just pull out the plugs and pump in
new grease thru the zerk till the new grease starts coming out of the plug
hole and replace the plugs.
Paul
I have an even older Wagner 7.5 HP motor with grease fittings on each end. Grease is a way to keep
something oiled without having to tend to it very often. Think of grease as it was originally . . .
oil absorbed into soap flakes.
Bob Swinney
Hi Ivan,
I used to run an early '60s Devlieg jig mill at work with a huge motor that
also had grease fittings at each end. We did (and still do) use grease in
it. Ours has plugs on the opposite side of the housing from the zerks that
need to be removed before new grease is added or you'll blow out the seals
and pump the motor full of grease. We just pull out the plugs and pump in
new grease thru the zerk till the new grease starts coming out of the plug
hole and replace the plugs.
Paul
Over lubrication is the primary cause of premature bearing failure.
Check out lube recommendations on the bearing or grease manufacturers
web site. Depending on the capacity of your grease gun usually a
couple of shots periodically will suffice.
Good point, Grant. I'd overlooked that.
Does anyone know of a book which describes the process of making grease
from oil and soap flakes? I'd be interested to read about it.
Best wishes,
Chris
The "soap" isn't necessarily something you would wash with. Lithium
is one "soap" used. So is Sodium, and Barium, as well as Calcium and
aluminum.
All the above are considered "soap" type greases.
I don't know of any grease in common use made from Lye soap (or Ivory
Snow)
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That depends on the size of the bearing. let's say for a 1/4"
ID bearing, the balls run at approximately a 1/2" diameter, and get the
SFM for that at 10,000 RPM as a starting point:
1309 SFM
Now -- let's take the shaft diameter up to say 2", and say perhaps
2-1/2" for the diameter of the bearing ball's path:
5208 SFM
And a really serious electric motor with a 6" shaft (you can guess the
horsepower rating if you wish), and probably 8" diameter bearing ball path:
20,943 SFM
So -- at what speed does the grease migration start to become a problem?
Assuming the 1039 SFM as the top acceptable one with the 1/4"
shaft, we get 625 RPM for the maximum speed for the 6" shaft.
And how big *do* electric motor shafts get? (Of course, the
larger ones do run slower to keep from self-disassembly. :-)
Enjoy,
DoN.
I don't think thermal conduction is the culprit. I am pretty sure that the
friction from churning the higher viscosity lubricant raises the
temperature. It is an effect not commonly thought of but you can get an idea
by running a power paint stirrer in thick paint. Essentially all of the
power it takes to spin the stirrer is converted to heat. I had a "bush-hog"
gearbox overheat and ruin the seals because I had put in oil which was too
thick.
Don Young
I'm thinking a few thousand horsepower for a 6" diameter shaft at 625
rpm, but that's just a guess.
I thought the issue Tom was talking about was the thermal insulating
effect of a thick grease barrier?
Well, I've seen alternators with 12" diameter shafts at a place where I
had a summer job once. But they had plain bearings. Hydrostatic when
starting, hydrodynamic when up to speed. Rumour has it than when the oil
pump is switched on, you can rotate a 90-ton rotor in those bearings by
hand. That's what I was told anyway.
Perhaps your reasoning explains why they don't use roller bearings in
those huge alternators, as they do 3,000 rpm. I just remember being told
that rolling element bearings didn't survive under those conditions.
I've also seen a ship with a half metre diameter propellor shaft
(apparently solid too).
Best wishes,
Chris
I've sometimes seen two maximum speeds quoted on bearing data sheets: a
lower speed for grease lubrication and a higher speed for oil
lubrication. I guess the advantage of oil is that it can circulate and
carry the heat away, so it doesn't have to rely heavily on thermal
conduction.
Best wishes,
Chris
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